Magnetic memory disks, such as the type typically used in a computer hard drive, have a smooth surface over which the read/write head flies during operation. The trend has been to reduce the fly height of the read/write head over the surface of the disk to increase the data recording density on the disk. While it is desirable for a read/write head to fly as close as possible to the surface of the disk, it is important that the read/write head does not contact the disk or defects on the surface of the disk. A defect on the surface of the disk that physically contacts the read/write head may damage the read/write head, the disk, or both. Consequently, care must be taken during the disk processing and testing to assure that there are no defects on the surface of the disk that are greater than the fly height of the read/write head, which today is approximately 1 .mu." (microinch).
Typical magnetic disks include an aluminum, glass, or silicon substrate that is plated with a NiP (nickel phosphate) layer and then textured, e.g., for the contact start stop zone. An underlayer of Cr (chromium) or NiP is sputtered on the plated NiP layer, a thin film of magnetic recording material, typically a Co (cobalt) alloy, is sputtered on the underlayer, followed by the deposition of a protective coating and a lubrication layer. The disk is then burnished to remove any asperities prior to testing the disk to assure the disk meets the required surface specifications. Presently, some magnetic disks are specified to have a roughness less than or equal to about 30 angstroms (3 nanometers).
A conventional method of burnishing the surfaces of a disk includes the use of an abrasive burnishing tape. FIG. 1 shows a portion of a conventional burnishing apparatus 10 including burnishing tape 12. The burnishing tape 12 is pressed against the surfaces of a disk 14 by pressure applying elements, such as pads 16. Pads 16 are mounted on mounting blocks 18 that are controlled by the burnishing apparatus to move towards or away from the surfaces of the disk 14, as indicated by arrows 19. Disk 14 is mounted on a spindle 20 that rotates disk 14 as indicated by arrow 22. Disk 14 and pads 16 move relative to each other, as indicated by arrow 24 so that a desired amount of the surfaces of disk 14 are burnished.
While pads 16 are shown in FIG. 1, it is understood by those of ordinary skill in the art that burnishing tape 12 may be pressed against the surfaces of the disk using other pressure applying elements, such as air knives, rollers, or other similar devices.
Once the surfaces of the disk are burnished, the disk is then tested, for example, with a glide head or certifying head. Conventionally, if there is a problem with the burnishing machine or the burnishing tape, the problem may not be recognized until after the burnishing process and the disk is tested. Meanwhile, additional disks may be burnished on the same burnishing machine and with the same burnishing tape.